For example, the surfaces of a fixture for fixing a board-mounted connector on a circuit board by soldering are generally subjected to tin (Sn) plating for improving solderability. However, it is being pointed out that in a case of soldering the fixture plated with Sn onto a circuit board, there is a fear that internal stress or external stress will act on a solder joint part, whereby needle-like crystals called whiskers will be generated, and the whiskers will cause short-circuiting between components around the fixture.
It is known that internal stress or external stress acting on an Sn plating layer as described above is related to generation of whiskers, and in Patent Document 1, there is disclosed a technology of forming recesses having depths, which are 0.4 times to 1.0 time the thickness of an Sn plating layer, in the plating layer, so as to relieve internal stress or external stress acting on the Sn plating layer by the recesses, thereby suppressing generation of whiskers.